An electronic element mounting substrate including a base body, an electrode, and a pad is known. The base body has a frame shape, and includes a first frame section and a second frame section, the second frame section having an inner surface that protrudes further inward than an inner surface of the first frame section when viewed in plan view. The electrode is disposed on a bottom surface of the first frame portion of the base body. The pad is disposed on a bottom surface of the second frame portion and is electrically connected to the electrode. Furthermore, an electronic device in which an electronic element is mounted on the electronic element mounting substrate and a top surface of the second frame section is covered by a lid is known, as disclosed in JP 2002-299592 A.
When mounting an electronic element or when bonding a lid to a base body, the electronic element or lid is generally mounted by pressing the electronic element or lid against the base body while applying heat. Increases in the performance of electronic elements have resulted in increases in the sizes thereof, and thus more heat is generated when the electronic elements are driven. If heat and stress arising during mounting or heat emitted when driving the electronic element act on the periphery of an opening in the electronic element mounting substrate, the periphery of the opening will likely deform. When the periphery of the opening in the electronic element mounting substrate deforms, there have been situations where stress concentration arises in the deformed area, producing cracks and fissures in the electronic element mounting substrate. There have been situations where such cracks and fissures have caused a drop in the airtightness of the electronic device, or the cracking has produced dust.
An electronic element mounting substrate according to one aspect of the present invention includes a base body, an electrode, and a pad. The base body has a frame shape, and includes a first frame section and a second frame section, the second frame section being disposed on the first frame section and including an inner surface protruding further inward than an inner surface of the first frame section when viewed in plan view. The electrode is disposed on a bottom surface of the first frame section of the base body. The pad is disposed on a bottom surface of a protruding part of the second frame section, and is electrically connected to the electrode. A groove extending in a vertical direction is formed in an inner surface of the protruding part of the second frame section of the base body.
An electronic device according to one aspect of the present invention includes the above-described electronic element mounting substrate, the electronic element mounted on the electronic element mounting substrate, and a lid bonded to a top surface of the electronic element mounting substrate.